44 Proceedings of the British Association. 



acid, potassa, and many oxysalts ; dilute sulphuric acid yielding 

 it in the greatest quantity, while no smell whatever was perceiv- 

 ed on the decomposition of solutions of hydracids, chlorides, bro- 

 mides, or iodides, which not only did not evolve it themselves, 

 but by their presence, even in small quantity, prevented its evo- 

 lution from solutions which would otherwise have produced it 

 abundantly. He found, on collecting the oxygen gas evolved at 

 the anode, from a solution capable of evolving the odor, that the 

 odor might be preserved for some time, by enclosing the gas in 

 well-stopped bottles. From the characters possessed by this oxy- 

 gen, he was led to consider the odor due to the presence of a 

 minute quantity of a new and hitherto wholly unknown sub- 

 stance, of considerable importance in many natural phenomena, 

 and he has therefore named it from its most evident character, 

 ozone. Its properties are briefly as follows : it is evolved only 

 from solutions containing it, by perfectly clean electrodes of pla- 

 tinum or gold ; whilst charcoal and the more oxidizable metals 

 are unable to cause its appearance. It can be obtained only from 

 a cold solution, as heat prevents its evolution. When a piece of 

 one of the oxidizable metals, such as zinc, tin, iron, mercury, &c., 

 or a few drops of solution of the protochloride of tin, or proto- 

 sulphate of iron, are placed in a portion of oxygen impregnated 

 with ozone, that peculiar substance is almost instantaneously ab- 

 sorbed ; and the oxygen becomes inodorous. When perfectly 

 clean and dry plates of gold or platinum are immersed in oxy- 

 gen containing ozone, they acquire a negatively electric state of 

 polarity : silver and copper also become thus electric, but in a far 

 less degree than gold or platinum. The plates thus polarized re- 

 tain their electric powers in air for a considerable time, but rapid- 

 ly lose it when plunged into hydrogen gas, in which, if retained 

 a sufficient time, they acquire an opposite state, becoming posi- 

 tively polarized. He then compares these eifects with those pro- 

 duced by the odorous matter peculiar to common electric sparks 

 and brushes. When a perfectly clean and dry plate of gold or 

 platinum is exposed to an electric brush issuing from a charged 

 and conducting point, it becomes positively polarized, and the 

 degree of polarity depends on the nature of the point and the 

 time which the plate has been exposed to the influence of the 

 brush issuing from it. He shows that the power is not due, to 

 the mere current of electricity escaping from the point, but to 



